Heretofore, a large number of image formation methods using a photopolymerization system have been known and used over a wide range of fields such as printing plate, printed circuit, hologram recording and three-dimensional formation.
For example, a printing plate is generally manufactured by a method such that a photopolymerizable composition comprising a compound having an addition-polymerizable ethylenic double bond, a photopolymerization initiator, an organic polymer compound and a thermal polymerization inhibitor is provided as a film layer on a support and exposed to a desired image to polymerization-cure the exposed area and the unexposed area is dissolution-removed to form a cured relief image.
Use of a copolymer of a (meth)acrylic acid and a (meth)acrylic acid ester as the organic polymer of the above-described composition is conventionally known in a large number of publications and described, for example, in JP-B-54-34327 (the term "JP-B" as used herein means an "examined Japanese paten publication"), JP-B-58-12577, JP-A-60-159743 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") and JP-A-60-208748.
Furthermore, JP-B-3-63740 describes the fact that the curing efficiency increases by using a copolymer of an allyl (meth)acrylate and a (meth)acrylic acid as the organic polymer of a photopolymerizable composition.
However, these conventional compositions have not yet succeeded in achieving sufficiently high capabilities and improvement is demanded particularly in view of sensitivity, degree of curing, developability and press life.
On the other hand, studies on high-sensitivity photosensitive materials using a photopolymerizable photosensitive material are advancing and such photosensitive materials are intended to be applied to various fields. Of those, particularly a laser direct plate-making system is being used in practice and to cope with this, a high-sensitivity photopolymer system capable of responding to the oscillation wavelength of a laser, for example, 488 nm of argon ion laser and 532 nm of FD-YAG laser, is keenly demanded.
Titanocene compounds are an effective metallocene compound photopolymerization initiator as described in JP-A-59-152396, JP-A-61-151197, JP-A-63-10602, JP-A-63-41484 and JP-A-3-12403, and examples of the combination use system thereof include a system of titanocene and a 3-ketocoumarin dye (see, JP-A-63-221110), a system comprising a combination of titanocene, a xanthene dye and further an addition-polymerizable ethylenically unsaturated compound containing an amino group or a urethane group (see, JP-A-4-221958 and JP-A-4-219756), and a system of titanocene and a specific merocyanine dye (see, JP-A-6-295061).
However, conventionally used photopolymerizable compositions cannot satisfy all capabilities such as sensitivity, degree of curing, developability and press life, in good balance.